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       Session PS-MoP

Paper PS-MoP14
Investigation on the Plasma Uniformity in Reactive Gas ECR Plasmas

Monday, October 29, 2001, 5:30 pm, Room 134/135

Session: Plasma Diagnostics and Plasma-Surface Interactions Poster Session
Presenter: M. Shindo, Kyushu University, Japan
Authors: M. Shindo, Kyushu University, Japan
Y. Kawai, Kyushu University, Japan
Correspondent: Click to Email
Reactive gas plasmas are widely used in etching process for fabricating ULSI. In order to reduce the production costs, a uniform and high-density plasma with a large diameter is required. An ECR plasma can be a candidate for such a plasma, since it easily reaches more than 10@super 12@cm@super -3@. In addition, one of the mechanism of the uniformity in an Ar ECR plasma was clarified by Ueda and Kawai.@footnote 1@ On the other hand, the transportation and diffusion mechanism in reactive gas plasmas become complicated since a large quantity of negative ions are produced. Thus, it is necessary to investigate the plasma uniformity under the existence of much negative ions. In this study, an attempt to measure the spatial distribution of charged species in O@sub 2@/Ar and C@sub 4@F@sub 8@/Ar ECR plasmas was made. Here, the density of negative ions was estimated from the phase velocity of the ion acoustic waves (fast mode) which were launched from a wire antenna to which the positive pulse voltages (30µ sec in duration time and V@sub pp@=40V) were applied, and were detected with a plane Langmuir probe biased at -90V. The detected signals were observed with an oscilloscope, and a trough and a crest were found, corresponding to the waves excited at the leading and falling edge, respectively. As a result, the negative ions existed near the wall rather than the center region. Moreover, it was found that the positive ion density was uniform in the center region, and the uniform area widened as the reactive gas mixture rate was increased. @FootnoteText@ @footnote 1@Y. Ueda and Y. Kawai, Appl. Phys. Lett.71 (1997) 2100.